At 88, 9-14 of the Journal of the Society of Dyers and Colourists (January 1972), an aqueous dyeing system is described in which exceptionally short liquor ratios are successfully employed by formulating the dyestuff with a foaming agent and converting the liquor to a foam on and in the substrate before raising temperature to fix the color. General application of the described technique for wet processing of all sorts is indicated.
The short liquor ratios involved (i.e., ratio of substrate weight to weight of treating liquor) are, in general, of the order at which no liquor exists outside the substrate following distribution of the treating liquor therein. For special purposes, such as to enable migration to occur during blend dyeing, it may sometimes be desirable to produce liquor outside the substrate by adding water to the system, but even so the liquor ratio employed will still be materially reduced from that usually employed in conventional dyeing and will normally be of the order first indicated.
Principal factors in obtaining effective application of treating formulations at such short liquor ratios are selection of a liquor ratio and foaming agent concentration at which distribution of the formulation through the substrate in a reasonable time is possible, and imposition of incidental mechanical forces on the substrate as it is handled during application of the formulation. In the latter connection, good results are reported for garments and half hose when treated with a dyestuff formulation in rotating drum equipment which subjects such articles to a tumbling action. Apparently such action generates a foamed condition of the applied formulation within the substrate that promotes excellent distribution.
The problem of providing a practicable application technique and apparatus arrangement for obtaining comparable results on piece goods and the like has remained, however, and it is the solution of this problem to which the present invention is directed.